197 auto level headlight issue

Hi everyone, my Clio 197 has projector headlights with auto levelling, but today I noticed that they where pointing upwards well above where they normally should be, as in lighting road signs up very brightly, then they would drop down to the floor. And back up again.

Had a look at the sensor at the rear of the car, which had clearly been bodged previously as one of the plastic clips had been broken off and was being held there with a cable tie!

Thinking I had found the problem I bodged it properly using a wood screw (best thing I could come up with) but seemed to work quite well. But the problem remains.

Just wondered if anyone else had experienced anything similar? Hoping it's not the sensor unit itself as it seems a bit pricey for what it is... (£100+!)

Thanks in advance!